Usage

morris – announcement (signal/event) system for Python

The morris module defines two main classes signal and SignalTestCase.

Defining Signals

Note

Since version 1.1 Signal.define and signal are identical

You can import the signal class and use idiomatic code like:

>>> from morris import signal

>>> # NOTE: classic python 2.x classes are not supported
>>> class Klass(object):
...     @signal
...     def on_foo(self):
...         pass

>>> @signal
... def on_bar():
...     pass

Connecting signal listeners

Connecting signals is equally easy, just call signal.connect()

>>> def handler():
...     print("handling signal")

>>> obj = Klass()
>>> obj.on_foo.connect(handler)
>>> on_bar.connect(handler)

Firing signals

To fire a signal simply call the signal object:

>>> obj.on_foo()
handling signal
>>> on_bar()
handling signal

Typically you will want to pass some additional arguments. Both positional and keyword arguments are supported:

>>> @signal
... def on_bar_with_args(arg1, arg2):
...     print("fired!")

>>> on_bar_with_args('foo', arg2='bar')
fired!

If you are working in a tight loop it is slightly faster to construct the list of positional arguments and the dictionary of keyword arguments and call the Signal.fire() method directly:

>>> args = ('foo',)
>>> kwargs = {'arg2': 'bar'}
>>> for i in range(3):
...     on_bar_with_args.fire(args, kwargs)
fired!
fired!
fired!

Passing additional meta-data to the signal listener

In some cases you may wish to use a generic signal handler that would benefit from knowing which signal has triggered it. To do that first make sure that your handler has a signal argument and then call sig.connect(handler, pass_signal=True):

>>> def generic_handler(*args, **kwargs):
...     signal = kwargs.pop('signal')
...     print("Handling signal {}: {} {}".format(signal, args, kwargs))

Let’s define two signals now:

>>> @signal
... def login(user, password):
...     pass
>>> @signal
... def logout(user):
...     pass

And connect both to the same handler:

>>> login.connect(generic_handler, pass_signal=True)
>>> logout.connect(generic_handler, pass_signal=True)

Now we can fire either one and see our handler work:

>>> login(str('user'), password=str('pass'))
Handling signal <signal name:'login'>: ('user',) {'password': 'pass'}
>>> logout(str('user'))
Handling signal <signal name:'logout'>: ('user',) {}

Note

The example uses str(...) to have identical output on Python 2.7 and 3.x but str() it is otherwise useless.

This also works with classes:

>>> class App(object):
...     def __repr__(self):
...         return "app"
...     @signal
...     def login(self, user, password):
...         pass
...     @signal
...     def logout(self, user):
...         pass
>>> app = App()
>>> app.login.connect(generic_handler, pass_signal=True)
>>> app.logout.connect(generic_handler, pass_signal=True)

We can now fire the signals, just as before:

>>> app.login(str('user'), password=str('pass'))
... # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
Handling signal <signal name:'...login' (specific to app)>:
    ('user',) {'password': 'pass'}
>>> app.logout(str('user'))  # doctest: +ELLIPSIS
Handling signal <signal name:'...logout' (specific to app)>: ('user',) {}

Disconnecting signals

To disconnect a signal handler call signal.disconnect() with the same listener object that was used in connect():

>>> obj.on_foo.disconnect(handler)
>>> on_bar.disconnect(handler)

Threading considerations

Morris doesn’t do anything related to threads. Threading is diverse enough that for now it was better to just let uses handle it. There are two things that are worth mentioning though:

1. signal.connect() and signal.disconnect() should be safe to call concurrently with signal.fire() since fire() operates on a copy of the list of listeners
2. Event handlers are called from the thread calling signal.fire(), not from the thread that was used to connect to the signal handler. If you need special provisions for working with signals in a specific thread consider calling a thread-library-specific function that calls a callable in a specific thread context.

Support for writing unit tests

Morris ships with support for writing tests for signals. You can use SignalTestCase’s support methods such as watchSignal(), assertSignalFired(), assertSignalNotFired() and assertSignalOrdering() to simplify your tests.

Here’s a simple example using all of the above:

>>> class App(object):
...     @signal
...     def on_login(self, user):
...         pass
...     @signal
...     def on_logout(self, user):
...         pass
...     def login(self, user):
...         self.on_login(user)
...     def logout(self, user):
...         self.on_logout(user)

>>> class AppTests(SignalTestCase):
...     def setUp(self):
...         self.app = App()
...         self.watchSignal(self.app.on_login)
...         self.watchSignal(self.app.on_logout)
...     def test_login(self):
...         # Log the user in, then out
...         self.app.login("user")
...         self.app.logout("user")
...         # Ensure that both login and logout signals were sent
...         event1 = self.assertSignalFired(self.app.on_login, 'user')
...         event2 = self.assertSignalFired(self.app.on_logout, 'user')
...         # Ensure that signals were fired in the right order
...         self.assertSignalOrdering(event1, event2)
...         # Ensure that we didn't login as admin
...         self.assertSignalNotFired(self.app.on_login, 'admin')

>>> import sys
>>> suite = unittest.TestLoader().loadTestsFromTestCase(AppTests)
>>> runner = unittest.TextTestRunner(stream=sys.stdout, verbosity=2)
>>> runner.run(suite)  # doctest: +ELLIPSIS
test_login (morris.AppTests) ... ok
<BLANKLINE>
----------------------------------------------------------------------
Ran 1 test in ...s
<BLANKLINE>
OK
<unittest.runner.TextTestResult run=1 errors=0 failures=0>

Implementation notes

At some point in time one may need to peek under the cover and understand where the list of signal listeners is being stored and how signals interact with classes. First of all, the signal class can be used as a Python descriptor. Descriptors are objects that have methods such as __get__, __set__ or __delete__.

You have most certainly used descriptors before, in fact the well-known @property decorator is nothing more than a class with methods such as listed above.

When used as a descriptor, a signal object will create new signal objects each time it is being accessed on an instance of some class. The instance of some class will be injected with a __signals__ dictionary that contains signals that have been accessed.

Consider this example:

>>> class Foo(object):
...     @signal
...     def ping(self):
...         pass

Here Foo.ping is one instance of signal. When that instance is being accessed on a class it simply returns itself.

>>> Foo.ping  # doctest: +ELLIPSIS
<signal name:'...ping'>

Note

While this looks similar to decorating a function it is functioning in a totally different way. Signals decorating plain functions (outside of a class definition body) are not using their descriptor nature.

Now, let’s instantiate Foo and see what’s inside:

>>> foo = Foo()
>>> foo.__dict__
{}

Nothing is inside, but there will be once we access foo.ping. Morris will create a new signal object associated with both the foo instance and the foo.ping method. It will look for foo.__signals__ and not having found any will create one from an empty dictionary. Lastly morris will add the newly created signal object to the dictionary. This way each time we access foo.ping (on the particular foo object) we’ll get exactly the same signal object in return.

>>> foo.ping  # doctest: +ELLIPSIS
<signal name:'...ping' (specific to <...Foo object at ...>)>
>>> foo.__dict__  # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
{'__signals__':
 {'...ping': <signal name:'...ping'
  (specific to <...Foo object at ...>)>}}

This all happens transparently the first time that code such as foo.ping.connect(...) is executed. When you connect a signal morris simply needs a place to store the list of listeners and that is in a signal object itself. We can now register a simple listener.

>>> def handler():
...     pass
>>> foo.ping.connect(handler)

Handlers are stored in the signal.listeners() attribute. They are stored as a list of listenerinfo tuples. Note that the first responder (the decorated function itself) is also present, here it is wrapped in the special (specific to morris) boundmethod class.

>>> foo.ping.listeners  # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
[listenerinfo(listener=<...boundmethod object at ...>, pass_signal=False),
 listenerinfo(listener=<function handler at ...>, pass_signal=False)]

Now, let’s compare this to using signals as a function decorator:

>>> @signal
... def standalone():
...     pass

The standalone() function is now replaced by the correspondingly-named signal object:

>>> standalone
<signal name:'standalone'>

The original function is connected as the first responder though:

>>> standalone.listeners  # doctest: +ELLIPSIS
[listenerinfo(listener=<function ...standalone at ...>, pass_signal=False)]

Since there are no extra objects, there is no __dict__ and no __signals__ either.

Using @signal on class with __slots__

Since (having read the previous section) you already know that signal descriptors access the __signals__ attribute on objects of classes they belong to, to use signals on a class that uses __slots__ you need to reserve the __signals__ slot up-front.

>>> class Slotted(object):
...     __slots__ = ('__signals__')
...     @signal
...     def ping(self):
...         pass
>>> Slotted.ping  # doctest: +ELLIPSIS
<signal name:'...ping'>
>>> slotted = Slotted()
>>> slotted.ping  # doctest: +ELLIPSIS
<signal name:'...ping' (specific to <...Slotted object at ...>)>
>>> slotted.__signals__  # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
{'...ping': <signal name:'...ping'
 (specific to <...Slotted object at ...>)>}

Creating signals explicitly

In all of the examples above we’ve been using signal as a decorator for existing methods or functions. This is fine for the vast majority of code but in some cases it may be beneficial to create signal objects explicitly. This may be of use in meta-programming, for example.

The signal class may be instantiated in the two following ways:

• with the signal name (and no listeners)
• with the first responder function (which becomes the first listener)

The second mode also has a special special case where the first responder. Let’s examine than now. First, the plain signal object:

>>> signal(str("my-signal"))
<signal name:'my-signal'>

This is a normal signal object, we can call it to fire the signal, we can use the signal.connect() method to add listeners, etc. If you want to create standalone signals, this is the best way to do it.

Now let’s examine the case where we pass a signal handler instead of the name:

>>> def my_signal2_handler():
...     pass
>>> signal(my_signal2_handler)
<signal name:'my_signal2_handler'>

Here the name of the signal is derived from the name of the handler function. We can customize the name, if desired, by passing the signal_name argument (preferably as a keyword argument to differentiate it from the pass_signal argument):

>>> signal(my_signal2_handler, signal_name='my-signal-2')
<signal name:'my-signal-2'>

Both examples that pass a handler are identical to what happens when decorating a regular function. There is nothing special about this mode either.

The last, and somewhat special, mode is where the handler is an instance of boundmethod (which is implemented inside morris). In the Python 2.x world, python had bound methods but they were removed. We still benefit from them, a little, hence they are back.

>>> class C(object):
...     def handler(self):
...         pass
>>> signal(boundmethod(C(), C.handler))  # doctest: +ELLIPSIS
<signal name:'...handler' (specific to <...C object at ...>)>

Note

It is possible to remove boundmethod and rely func.__self__ but this was not done, yet. Contributions are welcome!

To summarize this section, some simple rules:

• each signal object has a list of listeners
• signal objects act as descriptors and create per-instance signal objects
• signal object created this way are stored in per-instance __signals__ attribute

Reference

class morris.signal(name_or_first_responder, pass_signal=False, signal_name=None)

Basic signal that supports arbitrary listeners.

While this class can be used directly it is best used with the helper decorator Signal.define on a function or method. See the documentation for the morris module for details.

Attr _name:Name of the signal, typically accessed via name(). Attr _listeners:  List of signal listeners. Each item is a tuple (listener, pass_signal) that encodes how to call the listener.

__call__(*args, **kwargs)

Call fire() with all arguments forwarded transparently

This is provided for convenience so that a signal can be fired just by a simple method or function call and so that signals can be passed to other APIs that don’t understand the fire() method.

__get__(instance, owner)

Descriptor __get__ method

This method is called when a signal-decorated method is being accessed via an object or a class. It is never called for decorated functions.

Parameters:

• instance – Instance of the object the descriptor is being used on. This is None when the descriptor is accessed on a class.
• owner – The class that the descriptor is defined on.

Returns:

If instance is None we return ourselves, this is what descriptors typically do. If instance is not None we return a unique Signal instance that is specific to that object and signal. This is implemented by storing the signal inside the object’s __signals__ attribute.

__init__(name_or_first_responder, pass_signal=False, signal_name=None)

Construct a signal with the given name

Parameters:

• name_or_first_responder – Either the name of the signal to construct or a callable which will be the first responder. In the latter case the callable is used to obtain the name of the signal.
• pass_signal – An optional flag that instructs morris to pass the signal object itself to the first responder (as the signal argument). This is only used in the case where name_or_first_responder is a callable.
• signal_name – Optional name of the signal. This is meaningful only when the first argument name_or_first_responder is a callable. When that happens this argument is used and no guessing based on __qualname__ or __name__ is being used.

__repr__()

A representation of the signal.

There are two possible representations:

• a signal object created via a signal descriptor on an object
• a signal object acting as a descriptor or function decorator

__weakref__

list of weak references to the object (if defined)

connect(listener, pass_signal=False)

Connect a new listener to this signal

Parameters:

• listener – The listener (callable) to add
• pass_signal – An optional argument that controls if the signal object is explicitly passed to this listener when it is being fired. If enabled, a signal= keyword argument is passed to the listener function.

Returns:

None

The listener will be called whenever fire() or __call__() are called. The listener is appended to the list of listeners. Duplicates are not checked and if a listener is added twice it gets called twice.

define

alias of signal

disconnect(listener, pass_signal=False)

Disconnect an existing listener from this signal

Parameters:

• listener – The listener (callable) to remove
• pass_signal –

  An optional argument that controls if the signal object is explicitly passed to this listener when it is being fired. If enabled, a signal= keyword argument is passed to the listener function.

  Here, this argument simply aids in disconnecting the right listener. Make sure to pass the same value as was passed to connect()

Raises:

ValueError – If the listener (with the same value of pass_signal) is not present

Returns:

None

fire(args, kwargs)

Fire this signal with the specified arguments and keyword arguments.

Typically this is used by using __call__() on this object which is more natural as it does all the argument packing/unpacking transparently.

first_responder

The first responder function.

This is the function that the signal may have been instantiated with. It is only relevant if the signal itself is used as a descriptor in a class (where it decorates a method).

For example, contrast the access of the signal on the class and on a class instance:

>>> class C(object):
...     @signal
...     def on_foo(self):
...         pass

Class access gives uses the descriptor protocol to expose the actual signal object.

>>> C.on_foo  # doctest: +ELLIPSIS
<signal name:'...on_foo'>

Here we can use the first_responder property to see the actual function.

>>> C.on_foo.first_responder  # doctest: +ELLIPSIS
<function ...on_foo at ...>

Object access is different as now the signal instance is specific to the object:

>>> C().on_foo  # doctest: +ELLIPSIS
<signal name:'...on_foo' (specific to <morris.C object at ...)>

And now the first responder is gone (it is now buried inside the listeners() list):

>>> C().on_foo.first_responder

listeners

List of listenerinfo objects associated with this signal

The list of listeners is considered part of an implementation detail but is exposed for convenience. This is always the real list. Keep this in mind while connecting and disconnecting listeners. During the time fire() is called the list of listeners can be changed but won’t take effect until after fire() returns.

name

Name of the signal

For signals constructed manually (i.e. by calling Signal()) the name is arbitrary. For signals constructed using either Signal.define() or signal the name is obtained from the decorated function.

On python 3.3+ the qualified name is used (see PEP 3155), on earlier versions the plain name is used (without the class name). The name is identical regardless of how the signal is being accessed:

>>> class C(object):
...     @signal
...     def on_meth(self):
...         pass

As a descriptor on a class:

>>> C.on_meth.name  # doctest: +ELLIPSIS
'...on_meth'

As a descriptor on an object:

>>> C().on_meth.name  # doctest: +ELLIPSIS
'...on_meth'

As a decorated function:

>>> @signal
... def on_func():
...     pass
>>> on_func.name
'on_func'

signal_name

Name of the signal

For signals constructed manually (i.e. by calling Signal()) the name is arbitrary. For signals constructed using either Signal.define() or signal the name is obtained from the decorated function.

On python 3.3+ the qualified name is used (see PEP 3155), on earlier versions the plain name is used (without the class name). The name is identical regardless of how the signal is being accessed:

>>> class C(object):
...     @signal
...     def on_meth(self):
...         pass

As a descriptor on a class:

>>> C.on_meth.name  # doctest: +ELLIPSIS
'...on_meth'

As a descriptor on an object:

>>> C().on_meth.name  # doctest: +ELLIPSIS
'...on_meth'

As a decorated function:

>>> @signal
... def on_func():
...     pass
>>> on_func.name
'on_func'

class morris.SignalInterceptorMixIn

A mix-in class for TestCase-like classes that adds extra methods for working with and testing signals. This class may be of use if the base TestCase class is not the standard unittest.TestCase class but the user still wants to take advantage of the extra methods provided here.

assertSignalFired(signal, *args, **kwargs)

Assert that a signal was fired with appropriate arguments.

Parameters:

• signal – The Signal that should have been fired. Typically this is SomeClass.on_some_signal reference
• args – List of positional arguments passed to the signal handler
• kwargs – List of keyword arguments passed to the signal handler

Returns:

A 3-tuple (signal, args, kwargs) that describes that event

assertSignalNotFired(signal, *args, **kwargs)

Assert that a signal was fired with appropriate arguments.

Parameters:

• signal – The Signal that should not have been fired. Typically this is SomeClass.on_some_signal reference
• args – List of positional arguments passed to the signal handler
• kwargs – List of keyword arguments passed to the signal handler

assertSignalOrdering(*expected_events)

Assert that a signals were fired in a specific sequence.

Parameters:expected_events – A (varadic) list of events describing the signals that were fired Each element is a 3-tuple (signal, args, kwargs) that describes the event.

Note

If you are using assertSignalFired() then the return value of that method is a single event that can be passed to this method

watchSignal(signal)

Setup provisions to watch a specified signal

Parameters:signal – The Signal to watch for.

After calling this method you can use assertSignalFired() and assertSignalNotFired() with the same signal.

class morris.SignalTestCase(methodName='runTest')

Bases: unittest.case.TestCase, morris.SignalInterceptorMixIn

A unittest.TestCase subclass that simplifies testing uses of the Morris signals. It provides three assertion methods and one utility helper method for observing signal events.

addCleanup(**kwargs)

Add a function, with arguments, to be called when the test is completed. Functions added are called on a LIFO basis and are called after tearDown on test failure or success.

Cleanup items are called even if setUp fails (unlike tearDown).

addTypeEqualityFunc(typeobj, function)

Add a type specific assertEqual style function to compare a type.

This method is for use by TestCase subclasses that need to register their own type equality functions to provide nicer error messages.

Args:

typeobj: The data type to call this function on when both values

are of the same type in assertEqual().

function: The callable taking two arguments and an optional

msg= argument that raises self.failureException with a useful error message when the two arguments are not equal.

assertAlmostEqual(first, second, places=None, msg=None, delta=None)

Fail if the two objects are unequal as determined by their difference rounded to the given number of decimal places (default 7) and comparing to zero, or by comparing that the difference between the two objects is more than the given delta.

Note that decimal places (from zero) are usually not the same as significant digits (measured from the most significant digit).

If the two objects compare equal then they will automatically compare almost equal.

assertCountEqual(first, second, msg=None)

An unordered sequence comparison asserting that the same elements, regardless of order. If the same element occurs more than once, it verifies that the elements occur the same number of times.

self.assertEqual(Counter(list(first)),

Counter(list(second)))

Example:

• [0, 1, 1] and [1, 0, 1] compare equal.
• [0, 0, 1] and [0, 1] compare unequal.

assertDictContainsSubset(subset, dictionary, msg=None)

Checks whether dictionary is a superset of subset.

assertEqual(first, second, msg=None)

Fail if the two objects are unequal as determined by the ‘==’ operator.

assertFalse(expr, msg=None)

Check that the expression is false.

assertGreater(a, b, msg=None)

Just like self.assertTrue(a > b), but with a nicer default message.

assertGreaterEqual(a, b, msg=None)

Just like self.assertTrue(a >= b), but with a nicer default message.

assertIn(member, container, msg=None)

Just like self.assertTrue(a in b), but with a nicer default message.

assertIs(expr1, expr2, msg=None)

Just like self.assertTrue(a is b), but with a nicer default message.

assertIsInstance(obj, cls, msg=None)

Same as self.assertTrue(isinstance(obj, cls)), with a nicer default message.

assertIsNone(obj, msg=None)

Same as self.assertTrue(obj is None), with a nicer default message.

assertIsNot(expr1, expr2, msg=None)

Just like self.assertTrue(a is not b), but with a nicer default message.

assertIsNotNone(obj, msg=None)

Included for symmetry with assertIsNone.

assertLess(a, b, msg=None)

Just like self.assertTrue(a < b), but with a nicer default message.

assertLessEqual(a, b, msg=None)

Just like self.assertTrue(a <= b), but with a nicer default message.

assertListEqual(list1, list2, msg=None)

A list-specific equality assertion.

Args:

list1: The first list to compare. list2: The second list to compare. msg: Optional message to use on failure instead of a list of

differences.

assertLogs(logger=None, level=None)

Fail unless a log message of level level or higher is emitted on logger_name or its children. If omitted, level defaults to INFO and logger defaults to the root logger.

This method must be used as a context manager, and will yield a recording object with two attributes: output and records. At the end of the context manager, the output attribute will be a list of the matching formatted log messages and the records attribute will be a list of the corresponding LogRecord objects.

Example:

with self.assertLogs('foo', level='INFO') as cm:
    logging.getLogger('foo').info('first message')
    logging.getLogger('foo.bar').error('second message')
self.assertEqual(cm.output, ['INFO:foo:first message',
                             'ERROR:foo.bar:second message'])

assertMultiLineEqual(first, second, msg=None)

Assert that two multi-line strings are equal.

assertNotAlmostEqual(first, second, places=None, msg=None, delta=None)

Fail if the two objects are equal as determined by their difference rounded to the given number of decimal places (default 7) and comparing to zero, or by comparing that the difference between the two objects is less than the given delta.

Note that decimal places (from zero) are usually not the same as significant digits (measured from the most significant digit).

Objects that are equal automatically fail.

assertNotEqual(first, second, msg=None)

Fail if the two objects are equal as determined by the ‘!=’ operator.

assertNotIn(member, container, msg=None)

Just like self.assertTrue(a not in b), but with a nicer default message.

assertNotIsInstance(obj, cls, msg=None)

Included for symmetry with assertIsInstance.

assertNotRegex(text, unexpected_regex, msg=None)

Fail the test if the text matches the regular expression.

assertRaises(expected_exception, *args, **kwargs)

Fail unless an exception of class expected_exception is raised by the callable when invoked with specified positional and keyword arguments. If a different type of exception is raised, it will not be caught, and the test case will be deemed to have suffered an error, exactly as for an unexpected exception.

If called with the callable and arguments omitted, will return a context object used like this:

with self.assertRaises(SomeException):
    do_something()

An optional keyword argument ‘msg’ can be provided when assertRaises is used as a context object.

The context manager keeps a reference to the exception as the ‘exception’ attribute. This allows you to inspect the exception after the assertion:

with self.assertRaises(SomeException) as cm:
    do_something()
the_exception = cm.exception
self.assertEqual(the_exception.error_code, 3)

assertRaisesRegex(expected_exception, expected_regex, *args, **kwargs)

Asserts that the message in a raised exception matches a regex.

Args:

expected_exception: Exception class expected to be raised. expected_regex: Regex (re.Pattern object or string) expected

to be found in error message.

args: Function to be called and extra positional args. kwargs: Extra kwargs. msg: Optional message used in case of failure. Can only be used

when assertRaisesRegex is used as a context manager.

assertRegex(text, expected_regex, msg=None)

Fail the test unless the text matches the regular expression.

assertSequenceEqual(seq1, seq2, msg=None, seq_type=None)

An equality assertion for ordered sequences (like lists and tuples).

For the purposes of this function, a valid ordered sequence type is one which can be indexed, has a length, and has an equality operator.

Args:

seq1: The first sequence to compare. seq2: The second sequence to compare. seq_type: The expected datatype of the sequences, or None if no

datatype should be enforced.

msg: Optional message to use on failure instead of a list of

differences.

assertSetEqual(set1, set2, msg=None)

A set-specific equality assertion.

Args:

set1: The first set to compare. set2: The second set to compare. msg: Optional message to use on failure instead of a list of

differences.

assertSetEqual uses ducktyping to support different types of sets, and is optimized for sets specifically (parameters must support a difference method).

assertSignalFired(signal, *args, **kwargs)

Assert that a signal was fired with appropriate arguments.

Parameters:

• signal – The Signal that should have been fired. Typically this is SomeClass.on_some_signal reference
• args – List of positional arguments passed to the signal handler
• kwargs – List of keyword arguments passed to the signal handler

Returns:

A 3-tuple (signal, args, kwargs) that describes that event

assertSignalNotFired(signal, *args, **kwargs)

Assert that a signal was fired with appropriate arguments.

Parameters:

• signal – The Signal that should not have been fired. Typically this is SomeClass.on_some_signal reference
• args – List of positional arguments passed to the signal handler
• kwargs – List of keyword arguments passed to the signal handler

assertSignalOrdering(*expected_events)

Assert that a signals were fired in a specific sequence.

Parameters:expected_events – A (varadic) list of events describing the signals that were fired Each element is a 3-tuple (signal, args, kwargs) that describes the event.

Note

If you are using assertSignalFired() then the return value of that method is a single event that can be passed to this method

assertTrue(expr, msg=None)

Check that the expression is true.

assertTupleEqual(tuple1, tuple2, msg=None)

A tuple-specific equality assertion.

Args:

tuple1: The first tuple to compare. tuple2: The second tuple to compare. msg: Optional message to use on failure instead of a list of

differences.

assertWarns(expected_warning, *args, **kwargs)

Fail unless a warning of class warnClass is triggered by the callable when invoked with specified positional and keyword arguments. If a different type of warning is triggered, it will not be handled: depending on the other warning filtering rules in effect, it might be silenced, printed out, or raised as an exception.

If called with the callable and arguments omitted, will return a context object used like this:

with self.assertWarns(SomeWarning):
    do_something()

An optional keyword argument ‘msg’ can be provided when assertWarns is used as a context object.

The context manager keeps a reference to the first matching warning as the ‘warning’ attribute; similarly, the ‘filename’ and ‘lineno’ attributes give you information about the line of Python code from which the warning was triggered. This allows you to inspect the warning after the assertion:

with self.assertWarns(SomeWarning) as cm:
    do_something()
the_warning = cm.warning
self.assertEqual(the_warning.some_attribute, 147)

assertWarnsRegex(expected_warning, expected_regex, *args, **kwargs)

Asserts that the message in a triggered warning matches a regexp. Basic functioning is similar to assertWarns() with the addition that only warnings whose messages also match the regular expression are considered successful matches.

Args:

expected_warning: Warning class expected to be triggered. expected_regex: Regex (re.Pattern object or string) expected

to be found in error message.

args: Function to be called and extra positional args. kwargs: Extra kwargs. msg: Optional message used in case of failure. Can only be used

when assertWarnsRegex is used as a context manager.

debug()

Run the test without collecting errors in a TestResult

doCleanups()

Execute all cleanup functions. Normally called for you after tearDown.

fail(msg=None)

Fail immediately, with the given message.

failureException

alias of builtins.AssertionError

setUp()

Hook method for setting up the test fixture before exercising it.

classmethod setUpClass()

Hook method for setting up class fixture before running tests in the class.

shortDescription()

Returns a one-line description of the test, or None if no description has been provided.

The default implementation of this method returns the first line of the specified test method’s docstring.

skipTest(reason)

Skip this test.

subTest(msg=<object object>, **params)

Return a context manager that will return the enclosed block of code in a subtest identified by the optional message and keyword parameters. A failure in the subtest marks the test case as failed but resumes execution at the end of the enclosed block, allowing further test code to be executed.

tearDown()

Hook method for deconstructing the test fixture after testing it.

classmethod tearDownClass()

Hook method for deconstructing the class fixture after running all tests in the class.

watchSignal(signal)

Setup provisions to watch a specified signal

Parameters:signal – The Signal to watch for.

After calling this method you can use assertSignalFired() and assertSignalNotFired() with the same signal.

Internals

class morris.listenerinfo(listener, pass_signal)

count()

Return number of occurrences of value.

index()

Return first index of value.

Raises ValueError if the value is not present.

listener

Alias for field number 0

pass_signal

Alias for field number 1

class morris.boundmethod(instance, func)

A helper class that allows us to emulate a bound method

This class emulates a bond method by storing an object instance, function func and calling instance.``func``() whenever the boundmethod object itself is called.